Handheld electronic devices have become ubiquitous features of everyday life. Additionally, the capabilities of these devices have vastly increased in recent years. Typical examples of such devices are hand-held communication devices (such mobile telephones and so-called smart phones), personal digital assistants (PDA's), hand-held GPS and navigation systems, hand-held game console's, e-book readers, compact computing devices, video cameras, still cameras, and a vast array of other small electronic devices having view screens. It is particularly noted that the enumerated devices present convenient examples and that the invention should not be construed as being limited to these specific devices.
Increasingly many of these devices enable multi-media sourcing capabilities. In particular, many such devices are configured to enable video and/or image data to be provided to external devices. Conveniently, many such hand-held devices include features that rotate the displayed images depending on the viewing orientation used. Thus, the viewing orientation of the displayed image can be rotated depending on the viewing position of the user.
Additionally, it is becoming common to port these devices into other display devices, for example, desktop displays. Such hand held devices have some attributes that make such cross over to other displays a slightly more complicated endeavor.
As is known, an image frame comprises a set of pixels arranged in an array of rows and columns. Each frame having a width defined by the number of pixels in each horizontal row of pixels. The height is defined by the number of rows in each frame. Additionally, devices can display these images in so-called portrait and landscape viewing orientations. The formats display the images at right angles from each other. In one example, a “landscape” orientation (i.e., the screen is arranged having more y pixels than x pixels) of a hand-held display screen has a height to width ratio of less than 1, for example, a shown in FIG. 1(a). The image 101 is displayed in a landscape format. Other alternatives can use a default “portrait” orientation where the internal display screen is arranged having more x pixels than y pixels. Thus, having a height to width ratio of greater than 1. By way of example, FIG. 2(b) provides a portrait view of a similar image.
In the example of FIG. 1(a), a “raster scan” type of image reconstruction process can be used for an example display such as that of FIG. 1(b) showing a simplified expression of the process. For example, the image is displayed by scanning the image data from left to right 103 and from top to bottom starting in the upper left hand corner 102. The bottom row is scanned last.
When the display device uses a “landscape” view as the default, rotating the screen causes the image to tilt sideways. To correct this problem, many mobile or handheld devices have a rotation feature that compensates for this problem. Hence, and when the device is rotated, the image orientation changes to accommodate the rotation. For example, if the screen is rotated clock-wise 105 (see, FIG. 2(a)). Responsively, the depicted image is corrected by a counter-clockwise rotation 106 (see, FIG. 2(b)) to present a rendering image 111 that is viewable with a corrected orientation.
This works well when the image is viewed on the device screen. However, when the device is used as a source for an external display, this feature causes some problems. Due to the nature of the “raster scan” process, an incorrect image is generated when rendered on an external display.
For example, FIG. 2(c) illustrates how the image will be written from a handheld device (such as the image of FIG. 2(b)). The ordinary raster scanning process of the source works as before, scanning left to right. The problem is that the upper left 102 of the physical source screen was been rotates and now comprises the upper right 202 (of FIG. 2(c)) of the screen. This is problematic for a fixed default external display because the source process still scans from the source screen left to right. Accordingly, after rotation the scan process now proceeds from top to bottom progressing from right to left. This has the anticipated consequence, as illustrated in FIG. 2(d). When the skewed source data is received by the external display 211 and it is written across 213 the display screen in the usual fashion (raster scanned from upper left to upper right, then moving down a row and repeating). However, the pixels so scanned are oriented at a right angle thus displaying, a rotated image 212 rendered on the external display.
Among the aspects of the invention are method and adaptor embodiments enabling counter-rotation (also referred to herein as de-rotation) of rotated source images to enable correct image rendering by an external sink device.